Radar sensors are increasingly used in motor vehicles to determine distances and relative speeds with respect to preceding vehicles. They make distance warnings and adaptive cruise control (ACC) possible.
Such antenna arrays, which are also referred to as phased-array antennas, have significant directivity and thus allow the creation of angle-resolved radar sensors. The delay lines cause phase shifts between the waves emitted by the individual series-connected antenna elements. The antenna arrays are designed in such a way that constructive and destructive interference of the emitted waves results in a lobe-shaped directional characteristic of the radar field emitted by the antenna array at the radar frequency used by the radar sensor, e.g., in the range of 76 gigahertz (GHz). The formed directional lobe is able to be swiveled by varying the transmitting and receiving frequency.
Information regarding preceding vehicles may thus be acquired in an angle-resolved manner via frequency variation. The area in front of a motor vehicle may be scanned in a corresponding angle-resolved manner. However, the scanning times are long due to the swiveling of the directional lobes over the entire viewing angle. In addition, the surroundings are scanned at a particular instant at only a single swiveling angle corresponding to the width of the directional lobe.
A radar sensor including multiple independent antennas is described in German Patent Application No. DE 10 2006 032 540 A1. The antennas are situated offset in relation to an optical axis of a shared radar lens. Each individual antenna has a predefined directional characteristic, the antennas covering different angular ranges due to the configuration of the individual antennas and the shared radar lens. Simultaneous angle-resolved scanning of different angular ranges is possible in this manner, the radar sensor being configured in a mechanically complicated manner due to the use of independent antennas and the radar lens and the angular ranges not being able to be readily changed.